Licensing to practice in New Zealand is regulated by the Medical Council of New Zealand: INFO
With a Medical degree accredited by the General Medical Council of the UK or the Irish Medical Council, and a completed internship, you can apply for 'Provisional General Resistration'.
Provisional General Registration: you work under supervision and regular assessment restrictions for a period of time.
Link to information and to apply for Provisional General Registration: LINK
If you hold a formal postgraduate qualification (ie FRCA) from the UK or Ireland, you can apply for 'Vocational (specialist) Registration', which allows independant work.
To apply for Vocational Registration in Anaesthesia you must hold the equivilent of FANZCA: 2 years general medical experience
5 years advanced training in anaesthesia
Postgraduate exam equivilent to FANZCA
Link to information and to apply for Vocational Registration: LINK